Resistor units



Nov. 6, 1956 A. P. CHARBONNEAU 2,769,385

RESISTOR UNITS Filed April 26, 1954 3 Sheets-Sheet 2 i' 4%; WM I 2 IN V EN TOR.

Nov. 6, 1956 Filed April 26, 1954 A. P. CHARBONNEAU 2,769,885

RESISTOR UNITS 3 Sheets-Sheet 5 99110 P (Zaromze au firm/mg United States Patent O RESISTOR UNITS Allan P. Charbonneau, Wauwatosa, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware This invention relates to improvements in resistor units.

The invention relates more particularly to improvements in grid type resistor elements, frames for resistor units, and resistor units including said elements and frames.

A primary object of the invention is to provide resistor units which may be readily assembled and inexpensively manufactured.

Another object is to provide improved mounting means for resistor units.

Another object is to provide resistor units in which heating is minimized and which have improved means permitting expansion of the grids incident to the heating thereof.

Another object of the invention is to provide resistor units of the character described from which the grids may be removed without disturbing other similar units with which they may be stacked.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate an embodiment of the invention which will now be described, it being understood that certain modifications in respect of structure may be made in the embodiment illustrated without departing from the spirit of the invention or the scope of the appended claims.

In the drawings,

Figure 1 is a fragmentary view in front elevation of a resistor unit embodying the invention;

Fig. 2 is a fragmentary top plan view of one end portion of the resistor unit illustrated in Fig. 1;

Fig. 3 is a side elevational view of a preferred form of the terminal plate employed;

Fig. 4 is an end elevational view of the resistor unit illustrated in Fig. 1;

Fig. 5 is a side elevational view of a preferred form of the resistor grid employed; and

Fig. 6 is a perspective view of a preferred form of the insulating spacer employed.

Fig. 7 is a fragmentary view in top elevation of an alternative form of mounting means for resistor units;

Fig. 8 is a fragmentary view in front elevation of the mounting means illustrated in Fig. 7;

Fig. 9 is a view in front elevation of a preferred form of a resistor grid for use with the mounting means illustrated in Fig. 7; and

Fig. 10 is a view in front elevation of a preferred form of a terminal plate for use with the mounting means illustrated in Fig. 7.

These resistor units are in some respects similar to the resistor units described and claimed in my Patent No. 2,739,214, granted March 20, 1956, for Resistor Units and Method of Making the Same, and is an improvement thereover.

Referring to the drawings by reference numerals, the resistor unit shown comprises a plurality of like grids 10 which are stacked in zigzag fashion between a first pair, 12 and 14, and a second pair, 16 and 18, of insulating rods. Rods 12 and 14 are each attached at one end thereof to one bracket, and at the other end thereof to the other bracket of a pair of like brackets 20 and 22. These brackets are in turn fixedly attached to like end channel members 24 and 26, respectively. One end of each of rods 16 and 18 is attached to a bracket 28. The other end of each of rods 16 and 18 is attached to a bracket 30. Brackets 28 and 30 are alike and are slidably carried by channel members 24 and 26, respectively, in a manner permitting relative movement between such brackets and said channel members.

One of the grids 10 is shown in side elevation in Fig. 5. It consists of an integral element punched from a sheet of suitable resistance material such, for example as nickel chromium, copper nickel, or any suitable chrome-iron alloy. Grid 10 has a flat body portion 10 comprising a strip forming a series of closely spaced, oppositely projecting, parallel loops to form a relatively long circuitous resistance path of substantially uniform cross-sectional area. The body portion 10 bridges a pair of like, but oppositely projecting, lugs 10, 10, each of which is provided with spaced cutouts or notches 10 and 10. The body portion 10, of the grid shown, lies wholly on one side of the center line connecting a point midway between the cutouts 10 and 10 of one lug with a point midway between the cutouts 10 and 10 of the other lug 10.

The support rods 12, 14, 16 and 18 may be formed from insulating material but preferably comprise metal rods having threaded ends and having an insulating covering over all but the end portions of the rods, as best illustrated in Fig. 1. Rods 12 and 16 are held spaced a distance equal to the distance between the cutouts 10 and 10 or 10 and 10 of the lugs 19, 10 of the grids 10. The grids 10 are stacked on these rods with successive grids reversed so that the rods are disposed in the cutouts 10 10 of alternate grids and in the cutouts 10, 10 of the remaining grids. An appropriate number of insulating spacers 32 (see Fig. 6), having cutouts 32 and 32 corresponding in shape and spacing to cutouts 10 and 10 of lugs 10, 10 are inserted between certain adjacent lugs 10, 10 in such manner that rods 12 and 16 are disposed within one of cutouts 32, or 32. The spacers 32 are inserted between one lug 10 of each grid 10 and the adjacent lug 10 of its preceding grid 10, and between the other lugs 10, 10 of such preceding grid 10 and the adjacent lugs 10, 10 of the next preceding grid 10. Additional spacers 32 are disposed upon the ends of the rods 12 and 16 so that after compression of the stacks of grid lugs 10, 10 and spacers 32, such stacks will be substantialy co-extensive with the insulating covering of their respective rods. Metal connector or terminal plates 34, in which are formed cutouts 34 and 34 corresponding in'size and spacing to cutouts 10 and 10 of the lugs 10 and 10 and cutouts 32 and 32 of the spacers 32, are inserted in the stacks of grid lugs and spacers adjacent the outer lugs 10 of the end grids 10 and 10 Other plates 34 are inserted at selected points in the stacks of lugs and spacers alongside or between the lugs 10 or 10 of adjacent grids to provide resistor taps. Each plate 34 is provided with a tab 34 formed integrally with the body portion thereof. The tab is offset from the body portion. By reversing successive plates, maximum Working space, for connecting wires, etc., between plates is provided. The tabs 34 are perforated or otherwise adapted to accommodate wire fastening means generally designated 36.

The other cutout of each lug 16 or 10, spacer 32, and plate 34 is alined with the corresponding cutout of the other lugs, spacers and plates in its respective stack to form a groove in each stack. The rods 14 and 18 are each disposed within an associated one of these grooves,

' 3 The intermediate portion of each of brackets 20, 22, 28, and 30, is offset laterally and is provided with two perforations. Said perforations are spaced apart and are of a size to accommodate a corresponding pair of rods 1-2 and.14- or 16 and 18. The. ends of rods. 12. and 14.- are. insertedinthe perforations. of brackets 20-and22and the ends of rods 16 and 18 are inserted in the. perforations of brackets 28 and 30 in such manner as to. accommodate theends of bolts 16 and 18 and the respective nuts- 41), 4% between said brackets and the respective channel members 24-: and 26. Lock washers 38 andsaid nuts :1 are placed on each end: of each rod. and the nuts 40 are turned up. to compress the stacksof lugs 10*, 10, spacers 32, and plates 34. The plates 34-andthe adjacent lugs 10', 10 of adjacent grids 10, between which there are no spacers, are brought into contact with one another to form anelectrical connection therebetween. The grids. are thus. stacked in zigzag; fashion and form a. continuous zigzagv conductive path between the end grids 10 and 10 Referring again to Fig. 5, the cutouts 16 and 10 of each lug 10 or 111 are similar and the. body portion- 10' lies on one side of a line connecting the lugs midway between their respective cutouts. Also the body portion 10 lies wholly between the lugs. Thus shaped the grids are reversible in that all the grids are alike and successive grids of the stack may be reversed or inverted without possibility of the body portions 10 of adjacent grids 1 touching one another, while permitting minimum spacing between such grids. Moreover, the spacers 32: arereversible and their cutouts 32 and 392 are similar in. size and. shape to the cutouts 16 and of the grids 10. A most important advantage of thisconstruction is realized when the grids 10 are welded together at their respective lugs; Such welding is preferbaly accomplished prior to assembly of the grids and insulating spacersso that the welds may be made near the edge portions of the lugs closest to-their'respective body portions. This practice insures uniformity of the total resistance of manufactured units and alsominimized heating at the lugs. The construction herein disclosed permits such preferred welding without the consequent difiiculties encountered in prior resistance units, namely, the difficulty of threading the support rods alternately through insulating spacers and grid lugs. Such threading, is not required in assembling of the unit herein disclosed.

It will be apparent that plates. 34 may be omitted and that. the grids 1G or certain of them, may be integrally formed with tabssimilar to tabs 34 to accommodate wire attaching means 36. This may be, done Without sacrificing interchangeability or. reversibility of the. grids. Also the position, shape, and spacing of the cutouts of the grids, plates, and spacers may be altered without affecting such interchangeability and reversibility. When this feature is not required it will be obvious that many variations in the shape, size, and location of the cutouts and the integral gridtabs are possible without sacrificing the ease with which the support rods may be assembled with the grids and insulating spacers,.and without alteration of the. stacked relationship of the grids wherein the respective body portions of successive grids lie wholly on opposite sides of a transverse plane between such body portions.

The intermediate longitudinal portion. of each of channels 24 and 26 is offset laterally re-entrant of its channel, as. afore-indicated. One end of each channel 24 and 26 is provided with two openings. spaced to be alined with a similar pair of openings in the ends of brackets 20 and 22, respectively. The channels. and brackets are fastened together rigidly by fastening means 42- consisting of a nut, a lock washer, and. a bolt disposed in the alined openings. The ends of brackets 28 and 30 are provided with slots: 44 which open at that edge of the brackets toward the other ends: of each of the end channels 24 and 26. Shouldered pins 46; each. having a head 46, a shank 46 and an end 46 of reduced diameter, are inserted in openings in the end channels in such manner that the shank 46 of each is disposed within an associated slot 44 of the brackets 28, 30. The ends 46 of the pins are upset over the outer surface of the channels 24, 26, as shown at 46 and form a floating mounting for the brackets 28, 301 These brackets are free to slide over the pins 46 as the grids 10 expand and contract longitudinally as an incident to their heating and cooling.

Alternatively, the shouldered pin 45 may be attached to the bracket and the slot 44 may be formed" in the end channel. Either form permits withdrawal ofthe grid stack when fasteners 42 are removed Without altering the spacing of the end channels 24, 26. This feature is important especially in instances where several resistor units are stacked one on top of the other and the grids of a lower unit are desiredto. be. removed.

The width of'the. shanks, 46 of pins46. isonly slightly greater than the thickness. of the brackets, 28. and 30 so that heads 46? preventseparation of the channels 24' and. 26. Thus, support rods 12, 14, 16 and 18 serve not only to support and position the grid stacks. but also, serve to support the end. channels. 24 and 26; no other support rods being required.

Referring. to Figs. 7 and 8., the. mounting. means. there shown comprises an end channel member or end frame 160, a bracket. 102,. mounting rods 1114 and". 1%,.insulatingsleevesliii j and. 110 for rods 1114 and 10.6, a nut1'12 and. various other nuts, bolts. and washers.

Member 190" is channel-shaped. Its central, longitudinal. portion is, divided by a transverse slot. 114- into a main section 116 and. a relatively shorter upper section 118. The main and upper. sections. are oifset laterally in opposite directions from the. plane. of the longitudinal portion. The upper section. 118. is divided. into two tabs 120 and" 122 by a cutout 1'24 extending from the upper edge. 125 of channel member. to slot 114.

The resistor grids and the end terminal members. preferably are similar to thoseshown in Figs. 9- and and designated 142' and 144; respectively. These, together with suitable insulating spacers, are stacked on insulating sleeves 108 and 110. The stack of grids,.terminal' members and spacers on rod 104 and steeve 1198' are. compressed between a washer 130, an insulating washer 1'32, another washer 134, a lock washer 136, and a nut 112 at the respective ends of 'the stack.

Nut 112 is di'sposedwithin cutout 124' so that. the ends of tabs" and 122 are disposed in a groove 125 formed in the outer periphery of nut 112. The other ends of rod 104 and sleeve 198 and the other end channel'member of the resistor unit (none of'which is shown) are similarly constructed. and arranged. The groove 126 in nut 1'12 is wider than the thickness of the tabs. 12% and 122 to permit longitudinal expansion and contraction of rod 104, when the latter is heated and cooled, without flexing of the tabs 120 and 122 and to facilitate assembly and disassembly of the unit.

Nuts 112s1ide freely in the cutout 124. upon endwise expansion and contraction. of the resistor grids to change the spacing of rods 104 and 136 as an incident to heating of the resistor grids.

Rod 106 is fixedly mounted relatively to end channel member 100. It is secured, as by nuts, in a perforation in the cent'ralportion 1380f bracket 192. Portion 138 is offset laterally from the plane of the bracket in the direction of upper section 118 of the end' channel member 100. The ends of the bracket are secured to member 1% by nut and bolt sets 140.

I claim:

1. In a resistor unit, in combination, a plurality of resistor grids. each having, a pair of end lugs, each-of said lugs havinggformed therein a pair. of spaced. cutouts, each of saidgrids further having abodynporti'on. bridging. its pair of: lugs and lying; Wholiy onone side of a line ex.-

tending from a point midway between the cutouts of one lug to a point midway between the cutouts of the other lug, said grids being stacked with the body portions of successive grids reversed, a first pair of supporting rods each being disposed in an associated cutout of one lug of each of said grids, a second pair of support rods each being disposed in an associated cutout of the other lug of each of said grids.

2. The combination defined in claim 1 including a plurality of insulating spacers at least one of said spacers being disposed between a first lug of each grid except the end grids and the adjacent lug of its preceding grid and between the other lug of said preceding grid and the adjacent lug of its next preceding grid.

3. The combination defined in claim 2 including means to compress the stacks of lugs and spacers whereby the the second lug of each grid is electrically connected with said other lug of said preceding grid and the corresponding lug of said preceding grid is electrically connected with the other lug of said next preceding grid.

4. For a resistor comprising a plurality of resistor grids supported in stacked relation between parallel pairs of rods, a resistor support comprising said pairs of rods, a pair of end members having fixed spaced relationship, a pair of brackets fixedly attached to the respective ends of one of said pairs of rods, means to fixedly attach each of said brackets to an associated one of said end members, a second pair of brackets fixedly attached to the respective ends of the other pair of said support rods, and means comprising pins slidably connecting each bracket of said second pair of brackets to one of said end members whereby said second pair of brackets is free to move with respect to said end members as an incident to longitudinal expansion and/ or contraction of said grids.

5. In a resistor unit, in combination, a plurality of resistor grids each having a body portion bridging a pair of end lugs, said grids being stacked with the body portions of successive grids being reversed and lying wholly on opposite sides of a transverse plane to said body por tions, alternate lugs of successive grids each having a welded connection with a lug of the next succeeding grid, insulating spacers interposed between the other lugs of said successive grids forming parallel stacks of lugs and spacers, said stacks having said body portions of said grids stacked in zigzag fashion therebetween, said stacks having formed therein grooves on the outer surfaces thereof, and a support for said stacks comprising rods disposed one within each of said grooves.

6. The combination defined in claim 5 including connector plates disposed in at least one of said stacks of lugs adjacent selected lugs.

7. A resistor grid comprising an integral sheet punching having a pair of end mounting lugs each having cutout portions in opposite edge portions thereof and adapted for cooperation with suitable supporting members, said lugs being connected by a body portion lying wholly between the respective cutout portions of said lugs and on one side of the center line connecting a point midway between the cutout portions of one lug with a point midway between the cutout portions of the other lug, said body portion comprising a succession of parallel loops extending alternately in opposite directions in the plane thereof.

8. In a resistance unit, in combination, a plurality of like resistor grids each being symmetrical about a center line therethrough and having a body portion bridging a pair of end lugs extending laterally from said body portion, said grids being stacked in zigzag fashion with the body portions of successive grids lying wholly on opposite sides of a plane transverse to said body portions and the lugs of said grids lying in parallel stacks, said lugs each having a cutout portion in each of two edge portions thereof and alined with the corresponding cutout portions of each of the other of said lugs in its respective stack of logs, and a supporting frame for said grids comprising insulating rods each disposed in an associated one of the cutout portions of each of the lugs of the respective stacks of lugs.

9. A rame for a resistor unit, comprising, a pair of substantially channel-shaped end members arranged in parallel spaced relationship, each of said end members having a portion near one end thereof offset laterally away from the corresponding portion of the other, each of said end members having a portion near the other end thereof offset laterally toward the corresponding portion of the other, a pair of substantially U-shaped brackets each being attached to one of said end members at the portion first mentioned thereof and extending laterally therefrom toward one another, said portion second mentioned of each of said end members being provided with a cutout, a first resistor support rod secured at each end thereof to one of said brackets, a second resistor support rod extending between said end members, and means secured to the respective ends of said second resistor support rod and slidably disposed in an associated one of the cutouts of the end members, said cutouts being elongated in the plane of the said resistor support rods whereby the spacing between said resistor support rods may vary as an incident to expansion and contraction of the resistor mounted thereon.

10. A frame for a resistor unit comprising a pair of insulating support rods arranged in parallel, spaced relationship, a pair of U-shaped brackets secured to opposite ends of one of said rods and opening in the direction away from one another, a pair of connecting members each fastened to respective ends of the other of said rods, and a pair of end members arranged in parallel, spaced, back to back relationship, each of said end members having a portion at one end thereof oifset laterally away from the corresponding portion of the other, said brackets each being secured to an associated one of end members in bridging relationship to said offset portion thereof, each of said end members having a second portion at the opposite end thereof offset laterally toward the corresponding portion of the other and having a cutout opening at an edge of said portion and elongated toward said one of said rods, each of said connecting members being slidably disposed in an associated one of said cutouts.

References Cited in the file of this patent UNITED STATES PATENTS 1,860,493 Campbell May 31, 1932 2,128,222 Du Bois Aug. 30, 1938 2,680,178 Kuhn et a1. June 1, 1954 

